With two-thirds of the votes counted on Saturday, Museveni had about 69% of the ballots cast. Top rival Kizza Besigye had just shy of 25%.

Besigye has previously threatened Egypt-style protests if the results are not in line with what he and his supporters believe the true returns are.

On Saturday he rejected the official results projecting a large win for Museveni. "It is now clear the will of the people cannot be expressed through the electoral process," Besigye said. "We the Ugandan people will eventually prevail."

Electoral Commission chairman Badru Kiggundu said counting was going smoothly but he said there had been some problems on voting day. John Mary Odoy, director of Democracy Monitoring Group, said several abnormalities were reported during Friday's vote, including ballots pre-marked for Museveni's party and observers being refused access to polling stations. "There is no election in the world that is 100% without problems," Kiggundu said. "We are only five years into the current multiparty system."

Museveni, an ex-rebel commander who seized power at the head of a guerrilla army in 1986, once criticised African rulers who clung to power. But he sought another five-year term as a president who has fostered peace, stability and growth.

Museveni, who is vague about his age and is either 66 or 67, has mostly escaped the wrath recently aimed at other long-serving African leaders.

Besigye plans to release his own tally of results and is threatening Egypt-style unrest. He insists Uganda is ready for popular revolt. Museveni has said there will be no such protests in his country and that he will jail anyone who attempts to spark unrest.

While previous election campaigns were marred by violence against opposition candidates, observers say Museveni allowed opposition candidates a freer hand to campaign this year, perhaps thinking that allowing true competition would win him points with voters.